The present invention relates to a temperature control apparatus for an automotive vehicle or the like.
In such an apparatus, a heater and a cooler are disposed in a main air flow duct and either outside air or recirculated air is caused to flow through the duct by a blower. A temperature control door proportions the amount of air flowing through the heater and cooler and thereby controls the temperature of air which is introduced into a vehicle passenger compartment through an upper outlet or a lower outlet.
It is desirable for hygienic reasons to clean the air before it is discharged into the passenger compartment. The obvious solution is to mount a filter in the air flow duct. However, commercially available filters and activated charcoal units create so much resistance to air flow that a sufficient amount of air flow for temperature control cannot be passed through the duct without the utilization of an excessively large blower. For this reason, a bypass duct is provided which has an outlet communicating with the upper outlet of the main duct and an inlet communicating with the main duct upstream of the heater. A filter unit comprising an air filter and activated charcoal unit is mounted in the bypass duct. In this way, sufficient air is filtered to considerably improve the hygienic conditions inside the passenger compartment and the filtered air is discharged through the upper air outet which is closest to the occupants' faces.
However, a problem has existed in such an apparatus when operated in the heating mode. The filtered air which is discharged through the upper outlet is too cold for occupant comfort, with the discomfort being especially felt since the cold air is blown against the occupants' faces.